Method of forming round metal filaments



March 31, 1959 R. B. POND 2,879,566

METHOD OF FORMING ROUND METAL FILAMENTS Filed Feb. 16, 1956 UnitedStates Patent METHOD OF FORMING ROUND METAL FILAMENTS Robert B. Pond,Westminster, Md., assignor to Marvalaud, Incorporated, Westminster, Md.,a corporation of Maryland Application February 16, 1956, Serial No.565,813

14 Claims. (Cl. 22-2001) This invention relates to a method of producingmetal fibers and filaments.

Numerous methods have been employed in forming metal fibers andfilaments such as drawing a wire rod or extruding metal through suitableforming dies. Certain types of metals have been cast into grooves informing wire of various types. In my copending application Serial No.387,187, now Patent No. 2,825,108, there is disclosed a method offorming metal filaments by extruding a continuous stream of molten metaland impinging the stream on the concave surface of a rapidly rotatingchill plate or block. The chill block is formed of a metal of high heatconductivity and possesses suflicient mass or is provided with coolingmeans so as to dissipate the superheat and the heat of fusion of themetal as it impinges on the chill block. The molten stream of metal istransformed into a solid during a brief contact with the chill plate anda continuous filament is cast olf by the centrifugal force resultingfrom the rapid rotary motion.

The principal purpose of the present invention is to provide a simpleand novel method for the production of round filaments and fibers.

Other objects and advantages will be apparent from the drawing and thedescription thereof hereinafter.

The accompanying drawing illustrates the essential apparatus employed informing filaments and fibers in accordance with the present method.

This method involves extruding a continuous stream of molten metal anddirecting the stream into contact with a jet air or gas stream.

It is known that an unconfined high velocity or jet gas stream mayfunction as a solid body. It has been discovered that an unconfined highspeed column of gas or jet gas stream may be utilized to support acontinuous stream of molten metal until the molten metal has solidified.

As shown in the drawing, the jet stream of gas 1, such as air, may becreated by a sharp orifice 2 to which the gas is supplied by a suitableblower (not shown). The velocity of the gas at the point of dischargefrom the orifice may be as low as about 85 feet per second. The velocityutilized in any particular instance will be dependent more or less uponthe density of the metal being converted into fibers or filaments andthe degree of attenuation which it is desired to impart to the extrudedmetal, as will be explained hereinafter.

The continuous stream of molten metal may be provided by various means,such as an ejector tube 3 mountedin close proximity to the nozzle andprovided with a nozzle 4 having an extrusion orifice of the desiredsize. The ejector tube 3 communicates with a source of supply of themolten metal such as a reservoir 5 from which the flow of molten metalinto the ejector tube may be regulated by valve 6. Pressure is appliedto the molten metal so that it may be extruded from the ejector tube inthe form of a continuous stream of molten metal 8 as by supplying gasunder pressure through connature of product being produced.

Patented Mar. 31, 1959 duit 7 which communicates with a source of thegas. The orifice size, extrusion temperature, velocity and pressure ofthe molten metal are all factors affecting the size and shape of thefilament. In one example of the process disclosed in application SerialNumber 387,187 filed October 20, 1953 the orifice was made of glass withan aperture of 1.1.. The metal was heated to a temperature of 100 abovethe melting point and was ejected at 75 feet per second with 8 pounds ofpressure. Satisfactory filaments can be produced according to thepresent invention under these conditions. The metal may be extruded at avelocity of from about 10 feet per second to 100 feet per seconddepending upon the specific metal, the temperature of the molten metaland the type or The specific angle of contact between the molten metalstream and the jet gas stream is not particularly critical although itis preferred to extrude the molten metal at an acute angle with respectto the direction of movement of the air stream.

For example, if the velocity of the air stream and the velocity ofextrusion of the molten metal are substantially the same, for example,100 feet per second, the air stream merely supports the molten metalwhile it solidifies, and carries the solidified metal 9 a short distancebefore the pull of gravity on the metal overcomes the supporting forceof the jet air stream. The filament 9 then begins to fall. However, thehigh velocity stream of air creates air currents in the ambientatmosphere and the filament will be carried by an air current althoughthe filament is gradually settling. The filaments formed in accordancewith this invention are substantially round.

Although the stream of molten metal comes into contact with the highspeed jet stream of gas, the molten metal is not disintegrated oratomized. The metal in some instances appears to be supported by the jetair stream and in other cases it appears that the metal just enters thetop side of the air stream and is carried in this portion of the airstream without penetrating more than about one-fourth of the jet airstream. By-

decreasing the rate of extrusion of the molten metal or by increasingthe velocity of the jet air stream, the solidified portion of thefilament and that portion which, because of the pull of gravity, haspenetrated the jet air stream exerts a tension on the extruded moltenmetal and thereby attenuates the molten stream before the metal has setor solidified. It is possible, therefore, to form a filament ofappreciably smaller diameter than the diameter of the extruded metal. Afurther decrease in the velocity of extrusion or an increase in thevelocity of the air stream may be utilized to form fibers of desiredlengths.

In order to solidify the molten metal and form filaments or fibers, itis necessary to regulate the extrusion velocity and the velocity of thejet air stream to limit the penetration of the metal in the air streambefore Thus, the velocity of the air stream must be increased with anincrease in the density of the metal. As pointed out hereinbefore, wherethe molten metal is continuously extruded, the particular angle ofextrusion with respect to the direction of the jet air stream is notcritical and satisfactory filaments have been formed by extruding themolten metal stream at with respect to the jet air stream flow. As theangle is increased, it is noted, however, that the stream of metalimmediately adjacent the jet air stream assumes an armate path as itcontacts and just breaks through the surface of the jet air stream. Inmost instances, the metal stream and filament are carried on or in theupper portion of the jet air stream for a distance of not over aboutthree inches before the filament appears to deviate from a straightline.

Fibers ofv a substantially circular cross-section may be prepared fromnon-refractory metals which do not oxidize readily in air at thetemperatures required for extrusion. Satisfactory filaments and fibersof this type, for example, may be prepared from such metals as tin,lead, zinc and the like by extruding the molten metal at temperatures offrom about 1 C. to about 50 C. above their melting points and atpressures sufficient to extrude the metal continuously at the rate offrom about 50 feet per second to about 100 feet per second into a jetair stream having a velocity at the outlet of the jet of from about 85feet per second to about 100 feet per second. Although as illustrated inthe drawings and the description, the metal has been shown as beingextruded at the top of the jet air stream, it has been discovered thatsubstantially identical results may be obtained by extruding in anyother direction, such as in a horizontal direction toward the jet airstream or even in a vertical direction from be neath the jet air stream.

In view of the fact that the metal is either carried on the surface ofthe jet air stream or just in the jet air stream beneath the surfacewhile it is being transformed from a liquid to a solid condition, it ispossible to employ more than one extrusion chamber and space theextrusion chambers angularly around the nozzle 2. The metal of eachstream, while it is molten and immediately after it is solidified,remains at its respective position in or on the jet air stream and willnot come into contact with other molten metal streams or solidifiedfilaments until after the filaments leave the jet air stream and arecooled to a point below that at which the metal or metals weld together.

Although reference is made hereinbefore to tin, lead and zinc, thisinvention is not limited to the production of filamentary bodies (fibersand filaments) of these metals but is applicable to other non-refractorymetals such as, for example, iron and other ferrous metals, copper,aluminum, cadimum, bismuth, indium, magnesium and their alloys as wellas other metals and alloys which do not readily oxidize in their moltenconditions.

I claim:

1. The method of producing fibers and filaments which comprisesestablishing an unconfined jet gas stream, extrading a continuous streamof molten metal and directing the stream of molten metal into at leastpartial contact with the jet gas stream, the metal stream in a moltenstate penetrating not more than about one-fourth of the jet stream.

2. The method as defined in claim 1 wherein the stream of molten metalis directed into contact with the jet gas stream at an acute angle withrespect to the direction of gas flow.

3. The method as defined in claim 1 wherein the stream of molten metalis directed into contact with the jet gas stream at an angle not greaterthan 90 with respect to the direction of gas fiow.

4. The method as defined in claim 1 wherein the velocity of the jet gasstream is at least about 85 feet per second.

5. The method as defined in claim 1 wherein the velocity of extrusion ofthe molten metal is at least about 10 feet per second.

6. The method as defined in claim 1 wherein the velocity of extrusion ofthe molten metal is between about 10 feet per second and about 100 feetper second.

7. The method as defined in claim 1 wherein the velocity of the jet gasstream is at least about feet per second and the velocity of extrusionof the molten metal is between about 10 feet per second and about feetper second.

8. The method as defined in claim 1 wherein the velocity of the jet gasstream is at least about 85 feet per second, the molten metal is moltentin and the velocity of extrusion of the molten tin is between about 50feet per second and about 100 feet per second.

9. The method-as defined in claim 1 wherein the velocity of the jet gasstream is at least about 85 feet per second, the molten metal is moltenlead and the velocity of extrusion of the molten lead is between about50 feet per second and about 100 feet per second.

10. The method as defined in claim 1 wherein the velocity of the jet gasstream is at least about 85 feet per second, the molten metal is moltenzinc and the velocity of extrusion of the molten zinc is between about50 feet per second and about 100 feet per second.

11. The method of producing fibers and filaments which comprisesestablishing an unconfined jet gas stream, extruding a continuous streamof molten metal, directing the stream of molten metal into at leastpartial contact with the jet gas stream at such an angle that the metalstream in a molten state does not penetrate more than about one-fourthof the jet stream and carrying the stream of molten metal with the gasstream until the molten metal has been solidified.

12. The method as defined in claim 11 wherein the velocity of the jetgas stream is at least about 85 feet per second.

13. The method as defined in claim 11 wherein the velocity of extrusionof the molten metal is at least about 10 feet per second.

14. The method as defined in claim 11 wherein the velocity of the jetgas stream is at least about 85 feet per second and the velocity ofextrusion of the molten metal is between about 10 feet per second andabout 100 feet per second.

References Cited in the file of this patent UNITED STATES PATENTS279,346 Cookson June 12, 1883 745,786 Cole Dec. 1, 1903 1,092,934 MellenApr. 14, 1914 1,592,140 Horton et a1 July 13, 1926 2,489,242 Slayter etal. Nov. 22, 1949 2,639,490 Brennan May 26, 1953 2,717,416 FletcherSept. 13, 1955 FOREIGN PATENTS 4,391 Great Britain Sept. 15, 1882 46,293Germany Feb. 10, 1911

